X11 Forwarding over SSH w/ Putty

I am trying to forward X11 to my local computer using putty and ssh.
I have tried this before with another remote server on my local network and it worked fine.
Now I am trying the same with a remote server and I get the error message "Can;t open display localhost:0.0"

In putty I have set the machine to X11 port forwarding on localhost:0
I have also started an Cygwin X-Server on 0.0.
My DISPLAY variable on the remote machine is set to localhost:0.0